Metal beverage cans are designed and manufactured to withstand high internal pressure—typically 90 or 100 psi. Can bodies are commonly formed from a metal blank that is first drawn into a cup. The bottom of the cup is formed into a dome and a standing ring, and the sides of the cup are ironed to a desired can wall thickness and height. After the can is filled, a can end is placed onto the open can end and affixed with a seaming process.
It has been conventional practice to reduce the diameter at the top of the can to reduce the weight of the can end in a process referred to as necking. Cans may be necked in a “spin necking” process in which cans are rotated with rollers that reduce the diameter of the neck. Most cans are necked in a “die necking” process in which cans are longitudinally pushed into dies to gently reduce the neck diameter over several stages. For example, reducing the diameter of a can neck from a conventional body diameter of 2- 11/16th inches to 2- 6/16th inches (that is, from a 211 to a 206 size) often requires multiple stages.
For example, can manufacturing plants may need to combine two sections of can necking stages to reduce the neck of a can to a desired diameter. Typically, the two sections are combined with either a bridge transfer assembly or with a single base having a necking stage. Because floor space in a can manufacturing plant is limited, there is a need for effectively combining the two sections of can necking stages without unnecessarily wasting space.
Typical bridge transfer assemblies do not reduce the neck of the can as it transfers the can body from one section to the other. Accordingly, the space that the bridge transfer assembly occupies is not being used effectively, because it merely is passing the can body from one section of can necking stages to another without doing more.
Unlike the bridge transfer assembly, the single base having a necking stage reduces the end of the can body as it is passed from one section to the other. However, the single bases are large and bulky and often times take up an unnecessary amount of space.